The mechanism of control of prostaglandin synthesis will be investigated at a cellular level, with particular reference to the effect of Angiotensin II. The release of prostaglandin metabolites from the kidney into urine and renal venous blood will be measured, and evaluated as an index of renal synthesis of prostaglandins in vivo. The analytical approach will be stable isotope dilution, employing the multiple ion detector of the mass spectrometer. In addition, the application of a stable isotope method for PGE sub 2 to urine and renal venous plasma will be investigated. Factors governing renal prostaglandin synthesis in man will be investigated, and the possible role of prostaglandins in renal function during shock and with renal artery stenosis will be studied. The possible release of PGA sub 2 from the kidney as a humoral prostaglandin will be evaluated with specific chemical methods.